Premium Upgrade

Hey guys, I'm creating a website using wordpress and everytime I try to upgrade to premium I get a new blog created and the premium is assigned to that new blog. How can I upgrade my existing blog to premium. I've already spent a good amount of time trying to resolve this simple issue but I'm not being able to resolve it.
Please let me know as soon as you can because I have an urgency to finish this website, if not I'll have to look for a different alternative.
Thank you!!!